Solvent used in dry cleaning machines is commonly filtered to remove various contaminants. The filter cartridges employed in these machines ultimately must be replaced. Spent filter cartridges and other material such as lint containing hazardous solvents such as perchloroethylene (Perc), trichloroethane or trichloroethylene cannot normally be disposed of at ordinary solid waste disposal sites. These filter cartridges and other solvent contaminated materials must either be shipped, often at considerable expense, to a hazardous waste disposal site, or stripped of solvent to a "safe" level set by the EPA before they can be disposed of at a normal waste disposal site. This safe disposal level may be changed periodically as the EPA evaluates the environmental harm.
Steam is an easily produced and effective vehicle for stripping and reclaiming solvent from various materials, particularly when the solvent is immiscible with water. Perc is such a solvent, and others have rported the use of steam in various schemes to extract solvent from dry cleaning filters. The prior art discloses the adaptation of dry cleaning filter housings to receive steam thereby stripping filters in situ. For example, Tomes, U.S. Pat. No. 4,581,133, discloses a solvent reclaiming apparatus for stripping filter cartridges in situ, followed by distillation of the solvent (Perc), condensation and separation in a water solvent separator so that the solvent can be reclaimed. Filters treated as described by Tomes are reported to be contaminated with low enough levels of solvent to satisfy EPA requirements for disposal at an ordinary waste disposal site. Similarly, Fine, U.S. Pat. No. 4,513,590 discloses an apparatus which employs steam to strip filter cartridges in situ and to reclaim the solvent by condensation and separation. Fine simply passes enough steam through the cartridges until virtually all solvent has been removed. The Fine patent also discloses the use of an activated carbon bed to absorb solvent vapors during the filter stripping process.
Machines of the type described by Fine and Tomes must be added or adapted to fit each existing dry cleaning machine in order to strip filters of their solvent to meet EPA requirements. These machines are designed to strip filter cartridges in situ and therefore are unsuited for accepting exogenous filters, or other solvent contaminated materials such as lint. It can be seen that the prior art discloses machines that would add a substantial expense to each dry cleaning establishment and create unnecessary duplication of equipment.
Moreover, stripping filters in situ in their intact state requires substantial quantities of live steam which in turn produces substantial quantities of solvent contaminated water. Machines described in the prior art do not disclose how solvent contaminated water generated during the stripping process is to be handled. Without addressing this problem, the machines disclosed by Fines and Tomes would be rendered unsuitable since many localities have zero discharge requirements for perchloroethylene.
A need has therefore arisen for an environmentally sound solvent stripping and reclaiming apparatus which does not require that filters be stripped in situ. The apparatus should be capable of accepting filters from a variety of different dry cleaning machines as well as other material and should be flexible enough to meet changing EPA requirements. The apparatus should be inexpensive to operate, and not produce excessive quantities of solvent contaminated water. Finally, whatever solvent contaminated water is produced should be capable of meeting local discharge requirements.